Effect of bFGF on promoting angiogenesis in infarct area and improving myocardial fibrosis in mouse myocardial infarction model

AIM: To investigate the protective effect of basic fibroblast growth factor (bFGF) on the heart of mice with myocardial infarction and its mechanism. METHODS: The model of myocardial infarction was established by the ligation of left anterior descending artery of C57/B6 mice (8~12 weeks old) after lateral thoracotomy. The mice were divided into sham operation group, myocardial infarction group and bFGF administration group. bFGF at 0.5 μg was intraperitoneally injected on alternate days after myocardial infarction for 7 d. Cardiac Doppler ultrasonography was used to detect cardiac function after myocardial infarction for 28 d, and left ventricular end-diastolic diameter, left ventricular end-systolic diameter, left ventricular ejection fraction and left ventricular shortening fraction (LVFS) were used to evaluate cardiac function. After myocardial infarction for 28 d, the mice were sacrificed and the hearts were collected for preparing pathological sections. The degrees of myocardial fibrosis and angiogenesis in the myocardial infarction area were observed. Western blot was used to detect the indicators of angiogenesis. RESULTS: The results of Masson staining showed that bFGF administration significantly reduced myocardial fibrosis at 28 d after myocardial infarction. Cardiac ultrasound data showed that cardiac functions in myocardial infarction group were poorer than those in sham group, and bFGF administration significantly improved cardiac functions. Immunofluorescence staining showed that neovascularization in myocardial infarction area of bFGF administration group was more than that in myocardial infarction group. The results of Western blot showed that bFGF activated AKT/HIF-1α/VEGF signaling pathway. CONCLUSION: Intraperitoneal injection of bFGF reduces myocardial fibrosis and improves cardiac function in myocardial infarction mice. bFGF may promote angiogenesis by activating AKT/HIF-1α/VEGF signaling pathway.     

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Effect of galectin-3 on ventricular remodeling in rabbits with ischemic cardiac insufficiency

AIM:To investigate the relationship between galectin-3(Gal-3) and myocardial fibrosis,and to clarify the role of Gal-3 in ventricular remodeling in rabbits with ischemic cardiac insufficiency.METHODS:A rabbit model of ischemic cardiac insufficiency was established by ligation of the anterior descending branch of the coronary artery.The 20 rabbits were randomly divided into sham operation group and cardiac insufficiency group by random number table method.After 4 weeks of coronary artery ligation,the cardiac function was measured by cardiac echocardiogram.Real-time PCR and Western blot were used to detect the expression of Gal-3,type I collagen and type Ⅲ collagen at mRNA and protein levels in the myocardium.The serum Gal-3 contents were measured by ELISA.HE staining and Masson staining were used to observe the degree of fibrosis development in myocardial tissues after infarction.RESULTS:Compared with sham operation group,the mRNA expression of Gal-3 in cardiac insufficiency group was significantly increased.At the same time,type I collagen,type Ⅲ collagen and collagen type I/Ⅲ ratio were also increased significantly.The protein contents of Gal-3,type I collagen and type Ⅲ collagen were increased significantly.The serum Gal-3 levels were significantly increased.The pathological changes were observed in cardiac insufficiency group as the myocardial cell morphological disorder and marked hyperplasia of fibrous tissue were seen.CONCLUSION:Gal-3 aggravates myocardial fibrosis in rabbits with ischemic cardiac insufficiency,and promotes the ventricular remodeling and the occurrence of heart failure.     

Pathophysiological significance of ubiquition-proteasome system in myocardial infarction

Degradation of most proteins in eukaryotic cells is through the ubiquition-proteasome system (UPS). Recently, it demonstrated that UPS regulates cell apoptosis and cardiac hypertrophy. The differences of UPS regulation lie in E3 ligases, which specifically recognize targets and direct the ubiquitination process. Recent evidence suggests that atrogin-1/muscle atrophy F-box (Mafbx) and muscle RING finger 1 (MuRF1) may be critical mediators of the heart and muscle atrophy and hypertrophy. This review summarizes the possible relationship between UPS and cardiac dysfunction after myocardial infarction in order to inhibit cardiac dysfunction after myocardial infarction.     

Effects of diabetes on the development of heart failure in streptozotocin-induced diabetic rat model with acute myocardial infarction

AIM: To evaluate the time course and effect of diabetes on the development of heart failure (HF) in poorly controlled streptozotocin (STZ) -induced diabetic rat model for 70 d with acute myocardial infarction (AMI) in vivo. METHODS: All SD rats were randomized into four groups. Diabetes were induced by a single intraperitoneal injection of STZ (65 mg/kg), and 70 d later after the induction, AMI models were made with the ligation of left anterior descending coronary artery. The time course of diabetic effects on the development of heart failure in rats before and after AMI was observed. The survival rate of the rats and ultrastructure change of myocardium, the hemodynamics, the extent of the myocardial fibrosis, and the cardiac hypertrophy were also determined. RESULTS: After the ligation of left anterior descending coronary artery, the diabetic rats showed worse LV function and accelerated left ventricular (LV) remodeling compared with the non-diabetic ones. Myocardial fibrosis in both diabetic and non-diabetic rats subjected to AMI was similar in the early phase, while it was quite different after 1 month. CONCLUSION: Heart failure progression is accelerated in diabetic rat with AMI.     

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AIM: To investigate the contribution of angiotensin-converting enzyme inhibitor (ACEI) to the regulation of calpain system in infarcted myocardium. METHODS: Rat myocardial infarction (MI) model was established by permanent ligation of the left coronary artery. The treatment with the ACEI inhibitor rampril (1 mg·kg-1·d-1) was started 7 days prior to surgery. On day 1, 3, 7 and 14 after MI, protein levels of calpainⅠ, Ⅱ and calpastatin were determined in left ventricular free wall (LVFW), interventricular septum (IS) and right ventricule. RESULTS: CalpainⅠprotein level was increased in IS 14 d post MI, whereas the protein level of calpainⅡ was maximally increased in LVFW 3 d post MI. Rampril decreased protein up-regulation of calpainⅠ and Ⅱ, and reduced infarct size and interstitial fibrosis. Calpastatin protein expression was not affected by ACEI. CONCLUSIONS: CalpainⅠ is involved in cardiac remodelling in the late and calpainⅡ contributes to cardiac tissue damage in the early phase of MI. The heart protective effect of ACEI may be related to the inhibition of calpain system in the pathogenesis of myocardial infarction.     

Microparticles derived from bone marrow mesenchymal stem cells promote angiogenesis in rat myocardial infarction model

AIM: To observe the effects of microparticles derived from bone marrow mesenchymal stem cells (MSC-MPs) on angiogenesis and cardiac function in a rat myocardial infarction model. METHODS: MSCs were obtained from Sprague-Dawley rats. MSCs were treated under serum-free condition in hypoxia for 72 h, and the microparticles were isolated from the supernatants. The phenotypic profile of MSC-MPs was determined by bead-based flow cytometry and the morphology was observed under a transmission electron microscope. The rat myocardial infarction model was established. The cardiac function was evaluated by echocardiography after the intramyocardial injection of MSC-MPs. The myocardial infarct size was observed by Masson staining. The blood vessel density in the peri-infarcted area was measured using immunohistochemical staining for von Willebrand factor and α-smooth muscle actin. The expression of vascular endothelial growth factor (VEGF) was analyzed by real-time PCR. RESULTS: Apoptotic MSCs released a large quantity of microparticles which were phenotypically similar to the parent MSCs and 100~1 000 nm in diameter. The cardiac functions of myocardial infarction rat model were improved at 7 d and 28 d after intramyocardial injection of MSC-MPs compared with control group. The myocardial infarct size was reduced and angiogenesis was promoted significantly in the infarcted heart injected with MSC-MPs 28 d after treatment. MSC-MPs treatment also increased the expression level of VEGF within 7 d.CONCLUSION: MSC-MPs protect cardiac tissue from ischemic injury and improve cardiac function by promoting angiogenesis after myocardial infarction.     

Recent advances in Wnt-frizzled cascade and its relation to cardiovascular diseases

Many researches have focused on the Wnt-frizzled cascade in the recent years, while much work has been done in neoplastic diseases and embryology, the role of the Wnt-frizzled signal transduction pathway in cardiovascular diseases has only recently begun to be explored. It plays a very important role in many physiological and pathophysiological processes, such as its transduction pathway, the healing after myocardial infarction, the proliferation, differentiation and orientation of cardiomyocytes, angiogenesis/neovascularization, cardiac hypertrophy and heart failure, the deposition of the extracellular matrix and so on. This article is aimed at its relation with myocardial infarction and the role of this pathway in cardiovascular diseases.     

Effect of mesenchymal stem cells transfected with human heme oxygenase-1(HO-1)gene on myocardial apoptosis and angiogenesis

AIM: To investigate the effects of mesenchymal stem cells(MSCs)transfected with human heme oxygenase-1(HO-1)gene on myocardial apoptosis and angiogenesis. METHODS: MSCs were acquired from the bone marrow of adult rats. The cells were isolated, purified, cultured, and transfected with Adv-HO-1 in vitro before transplantation. At 1 h after left coronary artery ligation, Adv-HO-1-MSCs or MSCs were directly injected into the border of cardiac infarction in rats. Western blotting analysis was used to measure HO-1, and Bax protein expression in the border of cardiac infarction. ELISA was used to measure the expressions of VEGF and bFGF in the border of cardiac infarction. At 4 weeks after transplantation, the heart functions in survival rats were examined by the Buxco system. The rats were killed, then the myocardial infarct size was measured with Masson’s trichrome, and the expression of CD34 in myocardial infarction area was detected by immunohistochemical method. RESULTS: HO-1-MSCs exhibited increased HO-1 expression. The expression of HO-1, VEGF and bFGF in the border of cardiac infarction in the rats treated with HO-1-MSCs were higher than those in the rats treated with MSCs and PBS(P<0.01). However, the expression of apoptotic protein Bax was significantly lower than that in the rats treated with MSCs and PBS(P<0.01). The number of capillary vessels in the border of cardiac infarction in the rats treated with HO-1-MSCs was significantly higher than that in the rats treated with MSCs and PBS. The cardiac function in the rats treated with HO-1-MSCs was better than that in the rats treated with MSCs and PBS(P<0.01). CONCLUSION: The favorable effect on heart function appears to be a combined outcome of HO-1 and paracrine factors released by MSCs.     

Effects of metformin on pressure overload-induced cardiac hypertrophy in rats

AIM: To study the effects of metformin on the pressure overload-induced cardiac hypertrophy in rats. METHODS: Transverse aortic constriction (TAC) model of rat was made through laparotomy. One week after TAC surgery, the rats were randomly divided into 5 groups (n=8 in each group) and were administered with the corresponding drugs orally every day for 8 weeks: sham group (sham surgery, administered with 2 mL distilled water); TAC group (TAC rats, administered with 2 mL distilled water); metformin (MET) group (TAC rats, administered with MET at dose of 300 mg·kg^-1·d^-1); MN group [TAC rats, administered with MET at dose of 300 mg·kg^-1·d^-1 plus NOS inhibitor, N^G-nitro-L-arginine methyl ester (L-NAME) 50 mg·kg^-1·d^-1] and L-NAME group (TAC rats, administered with L-NAME at dose of 50 mg·kg^-1·d^-1). After treated for 8 weeks, the echocardiography, hemodynamics, the ratio of heart weight to body weight (HW/BW) and histological examination of the heart were performed. The levels of myocardial AMP-activated protein kinase subunit α (AMPKα), p-AMPKα Thr172, endothelial nitric oxide synthase (eNOS) and p-eNOS Ser1177 were detected by Western blotting. Plasma and myocardial nitric oxide (NO) were detected biochemically. RESULTS: After 8 weeks treatment, the wall thickness of left ventricle, the heart weight/body weight ratio (HW/BW), and the left ventricular myocardial perivascular fibrosis and myocardial interstitial fibrosis of the animals in TAC group were significantly increased as compared to those in sham rats. Treatment with MET for 8 weeks significantly attenuated left ventricular hypertrophy and improved cardiac function in TAC rats. These effects of MET were mostly abolished by L-NAME. Molecular biology and biochemical testing revealed that the levels of left ventricular myocardial p-AMPKα Thr172 and p-eNOS Ser1177, as well as the levels of myocardial and serum NO were significantly increased in MET group. CONCLUSION: Long-term MET treatment significantly inhibits the cardiac hypertrophy and the myocardial fibrosis and improves the cardiac functions in pressure-overload rats. The anti-hypertrophic effects of MET may be mediated via activation of AMPK-eNOS signaling pathway.     

Function and significance of integrin-linked kinase in heart

Integrin-linked kinase (ILK) is a widely expressed protein kinase that relate to cellular growth and differentiation. It is most abundant in the heart. Recently, many researches revealed that ILK is highly relevant to cardiac response to biomechanical stresses. Also, ILK plays important roles in regulation of the occurrence and development of cardiac hypertrophy, dilated cardiomyopathy, viral myocarditis and myocardial senescence via correlation to several classical signal transduction pathway. Meanwhile, ILK functions in protection after myocardial infarction. This article will try to summarize the effects and relevant mechanism of ILK in above-mentioned aspects, overall reveals the roles of ILK in heart and its potential clinical significance.     

Effects of different ages on ventricular remodeling after ischemic heart failure in mice

AIM: To observe ventricular remodeling induced by ischemic heart failure in the mice at different ages.METHODS: Three-month-old (young group, n=50) and 18-month-old (old group, n=50) male C57BL/6J mice were selected in the study. Forty mice underwent ligation of left coronary artery with certain infarct size, and 10 were sham-operated for control. Echocardiography was performed after 8 weeks of infarction. All mice were killed and the hearts were collected for examinations. Masson trichrome staining was used to detect myocardial fibrosis. The expression of type I and type Ⅲ collagens was measured by the method of immunohistochemistry.RESULTS: The incidences of cardiac rupture (18% vs 10%, P<0.05) and heart failure (22% vs 10%, P<0.05) were significantly higher in aged mice than those in young mice. The degrees of left ventricular dilation, contractile dysfunction and heart rate were significantly higher in aged mice than those in young mice (P<0.05). The left ventricular mass index, collagen volume fraction, the expression of type I collagen and ratio of type Ⅰ/Ⅲ collagens were significantly increased in aged mice as compared with young mice (P<0.05).CONCLUSION: After heart failure, aged mice show abnormal collagen distribution, and suffer from worse cardiac functions and more serious ventricular remodeling.     

Relationship between NLRP3 inflammasome-IL-1β axis and End-MT after acute myocardial infarction in rats

AIM: To investigate whether activation of NLRP3 inflammasome-IL-1β axis is consistent with endothelial-mesenchymal transition (End-MT) during the process of myocardial fibrosis after acute myocardial infarction (AMI). METHODS: Adult male SD rats (n=30) were randomly divided into sham operation group (n=15) and AMI group (n=15). After 28 d, Masson staining was used to detect the level of myocardial fibrosis. The activation of NLRP3 inflammasome including NLRP3, ASC, pro-caspase-1 and caspase-1, the endothelial cell markers CD31 and VE-cadherin, and the mesenchymal cell markers α-SMA and FSP1 were analyzed by Western blot. The expression of IL-1β was measured by ELISA. RESULTS: The levels of myocardial fibrosis and End-MT, the activation of NLRP3 inflammasome, and the expression of caspase-1 and IL-1β were significantly increased in AMI group compared with sham operation group (P<0.05). CONCLUSION: The activation of NLRP3 inflammasome-IL-1β axis is significantly consistent with End-MT process, suggesting that NLRP3 inflammasome-IL-1β, as a potential target for the activation of End-MT, will provide a novel theoretical target for the treatment of myocardial fibrosis and heart failure after AMI.     

Role of nucleolin on myocardial hypertrophy and fibrosis in type Ⅱ diabetic cardiomyopathy mice

AIM:To investigate the effect of nucleolin on diabetic cardiomyopathy in mice.METHODS:A type Ⅱ diabetic cardiomyopathy mouse model was prepared using a cardiac-specific nucleolin-overexpressing transgenic mice.The mice were divided into wild-type mouse control group,nucleolin transgenic mouse control group,wild-type mouse diabetes group and nucleolin transgenic mouse diabetes group.Wheat germ agglutinin (WGA) fluorescent dye,Masson staining and PowerLab system detection were used to further clarify the role of nucleolin on cardiac hypertrophy,fibrosis and cardiac function in type Ⅱ diabetic cardiomyopathy mice.RESULTS:Compared with wild-type mouse control group,no significant increase in blood glucose level was found,while genetical myocardial cell hypertrophy was significantly attenuated in nucleolin transgenic mouse diabetes group.The collagen fibers were also significantly reduced,and hemodynamic indexes±dp/dt_max,left ventricular end-diastolic pressure,left ventricular systolic pressure and heart rate were also improved.The above differences were statistically significant.CONCLUSION:Nucleolin may reduce the occurrence of myocardial hypertrophy and fibrosis,thus improving the cardiac function of diabetic cardiomyopathy mice.     

Transplantation of bcl-2 gene-modified bone marrow mesenchymal stem cells improves cardiac function and angiogenesis in rabbit ischemic car-diac insufficiency model

AIM: To investigate the effects of transplantation of bone marrow mesenchymal stem cells (BMSCs) modified by bcl-2 gene on myocardial cell apoptosis, angiogenesis and cardiac function in the rabbit after acute myocardial infarction (MI).METHODS: The rabbit BMSCs were isolated, cultured and purified in vitro. The BMSCs were transfected with adenovirus or adenovirus-Bcl-2. The rabbit model of MI was established by ligation of left anterior descending branch. The rabbits were injected with Ad-Bcl-2-BMSCs (MI+Bcl-2-BMSCs group), Ad-BMSCs (MI+BMSCs group) and DMEM (MI group) in infarction marginal zone 2 weeks after ligation. The cardiac function was evaluated by echocardiography.The apoptosis of myocardial cells was measured by TUNEL. The mRNA expression of VEGF was detected by real-time PCR. The expression of CD31 was examined by immunohistochemical staining, and new blood capillaries were counted at 4 weeks after BMSCs transplantation. The correlation of the above values with cardiac function was analyzed.RESULTS: The cardiac function was better, the apoptotic rate was lower, the mRNA expression of VEGF and the capillary density were higher in both MI+Bcl-2-BMSCs group and the MI+BMSCs group than those in MI group, and those in MI+Bcl-2-BMSCs group increased more obviously.The left ventricular ejection fraction (LVEF) had a negative correlation with the myocardial cell apoptosis rate. A positive correlation with the mRNA expression level of VEGF and the capillary density was also observed.CONCLUSION: The transplantation of BMSCs modified by bcl-2 gene significantly reduces the myocardial cell apoptosis, promotes angiogenesis, improves heart function of the rabbits with MI.     

Effect of pretreatment with 11,12-EET on myocardial ischemia/reperfusion injury in rats

AIM: To examine the effect of pretreatment with low-concentration of 11, 12-epoxyeicosatrienoic acid(EET) on myocardial ischemia/reperfusion injury in rats. METHODS: After tracheotomy, myocardial ischemia/reperfusion was produced by occlusion and release of the left anterior descending artery(LAD) of the rats. Ischemic preconditioning(IP) was made by two times of ischemia(5 min)/reperfusion(5 min). The experiment was conducted in three groups: control,IP and pretreatment with 11,12-EET(6.24×10^-8 mol/L), and each group was subdivided into two subgroups:A,the rats were subjected to ischemia(10 min)/reperfusion(10 min) and arrhythmias during the whole periods were monitored; The rats in B were subjected to ischemia(60 min)/reperfusion(30 min) and arrhythmias, cardiac funtion and myocardial infarction size were documented. RESULTS: Both IP and pretreatment with 11,12-EET could protect the heart against arrhythmias, cardiac disfunction and myocardial infarction. CONCLUSION: Pretreatment with 11,12-EET had protective effect on myocardium in case of ischemia/reperfusion, which was similar to ischemic preconditioning.     

Inhibitory effect of aerobic exercise on left ventricular remodeling and sympathetic neural remodeling in rats with heart failure after myocardial infarction

AIM: To investigate the effects of long-term aerobic exercise on the heart and sympathetic neural remodeling (structure and function remodeling) in heart failure rats induced by myocardial infarction. METHODS: Heart failure model after myocardial infarction was performed by ligating anterior descending coronary artery in the Wistar rats. Four weeks after operation, the rats were randomly divided into sham operation sedentary (S) group, heart failure sedentary (H) group and heart failure exercise (HE) group. The animals in HE group underwent 10-week treadmill running, while those in S group and H group were sustained in a resting state. The cardiac structure and function including left ventricular internal diameter at diastole (LVIDd), left ventricular internal diameter at systole (LVIDs), left ventricular anterior wall diameter at diastole (LVAWDd), left ventricular anterior wall diameter at systole (LVAWDs), left ventricular posterior wall diameter at diastole (LVPWDd) and left ventricular posterior wall diameter at systole (LVPWDs), and cardiac function parameters including fractional shortening (FS) and left ventricular ejection fraction (LVEF) were measured by echocardiography. The myocardium was collected for histopathological observation with Masson staining, and the collagen volume fraction (CVF) was determined. The concentrations of norepinephrine (NE) in the myocardium and plasma were measured by high-pressure liquid chromatography. The frequency domain analysis was applied for determining the heart rate variability (HRV) via subcutaneous recording electrode involving total power (TP), normalized low power (LFn), normalized high power (HFn) and LF/HF ratio. The mRNA expression of collagen type I (Col-I), collagen type III (Col-III), atrial natriuretic factor (ANF), α-myosin heavy chain (α-MHC), β-myosin heavy chain (β-MHC), sarcoplasmic endoplasmic reticulum Ca²⁺-ATPase (SERCA2a) was detected by real-time PCR. The protein levels of nerve growth factor (NGF) and its receptor (TrkA), and tyrosine hydroxylase (TH) were measured by Western blotting. RESULTS: (1) Compared with S group, body weight (BW), LVIDd, FS, LVEF, TP, HFn, the mRNA expression of α-MHC and SERCA2a, and the protein levels of NGF, TrkA and TH decreased (P<0.05). Left ventricular weight (LVW), left ventricular mass index (LVMI), LVAWDd, LVAWDs, LVPWDd, LVPWDs, CVF, plasma and myocardial NE content, LFn, LF/HF, and the mRNA expression of ANF, β-MHC, Col-I and Col-III increased (P<0.05) in H group. (2) Compared with H group, LVW, LVMI, LVIDd, FS, LVEF, TP, HFn, the mRNA expression of α-MHC and SERCA2a, and the protein levels of NGF, TrkA and TH were raised (P<0.05), while CVF, plasma and myocardial NE content, LFn, LF/HF, and the mRNA expression of ANF, β-MHC, Col-I and Col-III decreased (P<0.05) in HE group. CONCLUSION: Long-term aerobic exercise training leads to inhibition of heart and sympathetic neural remodeling and improvement of cardiac function and autonomic modulation in the rats after myocardial infarction.     

Effect of endoplasmic reticulum stress on cardiac myocyte apoptosis in mouse congestive heart failure induced by myocardial infraction

AIM: To explore the effect of endoplasmic reticulum stress on cardiac myocyte apoptosis in mouse congestive heart failure induced by myocardial infraction.METHODS: The mouse model of heart failure was established by ligating the left anterior descending coronary to produce acute myocardial infarction. Thirty-two mice were divided into 4 groups: sham group and groups of post-operation at time points of 2, 4 or 6 weeks, respectively. The ventricular dilatation and left ventricular functions were assessed by echocardiography. The expression of GRP78, CHOP, caspase-12, cleaved caspase-12, JNK and phosphorylated-JNK was detected by Western blotting. The cardiac myocyte apoptosis was determined by terminal deoxynucleotidyl transferase mediated dUTP-biotin nick end labeling (TUNEL).RESULTS: The cardiac expression of endoplasmic reticulum chaperones GRP78 was significantly increased in the hearts with functional failure. The upregulated expression of CHOP, phosphorylated-JNK and cleaved caspase-12 illuminated that the CHOP-JNK- caspase-12 dependent pathways for endoplasmic reticulum-initiated apoptosis were activated in the heart with functional failure by myocardial infraction. CONCLUSION: These findings suggest that the congestive heart failure induced by myocardial infraction is associated with endoplasmic reticulum stress and activation of CHOP, JNK, caspase-12 dependent pathways for endoplasmic reticulum-initiated apoptosis.